GRAS 40DD 1/8″ Prepolarized Pressure Microphone

Introduction

The 40DD is an IEC 61094 1/8″ prepolarized pressure microphone with rear-venting. Read about the externally polarized equivalent GRAS 40DP

It is a high-precision condenser microphone made according to IEC 61094-4 requirements. Its tiny size allows it to be used for measuring very high frequency sounds without disturbing the sound field. It can measure sound pressure levels up to 174 dB in the range of 6 Hz to 140 kHz.

40DD is individually factory-calibrated and delivered with a calibration chart stating its specific open-circuit sensitivity and pressure frequency response.

A front-vented version is available, 40DD-FV 1/8” Prepolarized Pressure Microphone, Front Vented.

Typical applications and use

The 40DD has a low sensitivity making it perfect for sound measurements at high frequencies and very high level pressure, as well as impulse noises.

The 40DD is included in the 67SB Blast Probe Microphone because of its wide-frequency response.

Compatibility

The 40DD must be used with an adapter for mounting a 1/8″ microphone onto a 1/4″ preamplifier.

System verification

For daily verification and check of your measurement setup, we recommend using a calibrator like GRAS GRAS 42AG Multifunction Sound Level Calibrator.

For proper sensitivity calibration, we recommend using a pistonphone like GRAS Intelligent Pistonphone GRAS 42AP.

Calibration

When leaving the factory, all GRAS microphones have been calibrated in a controlled laboratory environment using traceable calibration equipment. Depending on the use, measurement environment and internal quality control programs we recommend that the microphone is recalibrated at least once a year.

We offer two kinds of calibration as an optional after-sales service: GRAS Traceable Calibration and GRAS Accredited Calibration.

GRAS Traceable Calibration is a traceable calibration performed by trained personnel under controlled conditions according to established procedures and standards. This is identical to the rigorous calibration that all GRAS microphones are subjected to as an integral part of our quality assurance.

GRAS Accredited Calibration is performed by the GRAS Accredited Calibration Laboratory that has been accredited in accordance with ISO 17025 by DANAK, the Danish Accreditation Fund.

If you want a new microphone set delivered with an accredited calibration in stead of the default factory calibration, specify this when ordering.

Learn more at gras/calib.

Quality and warranty

All GRAS microphones are made of high-quality materials that will ensure life-long stability and robustness. The microphones are all assembled in verified clean-room environments by skilled and dedicated operators with many years of expertise in this field.

The microphone diaphragm, body, and improved protection grid are made of high-grade stainless steel, which makes the microphone resistant to physical damage, as well as corrosion caused by aggressive air or gasses.

This, combined with the reinforced gold-plated microphone terminal which guarantees a highly reliable connection, enables GRAS to offer 5 years warranty against defective materials and workmanship.

Service

If you accidentally damage the diaphragm on a GRAS microphone, we can—in most cases—replace it at a very reasonable cost and with a short turn-around time. This not only protects your investment, but also pleases your quality assurance department because you don’t have to worry about new serial numbers, etc.